Antimicrobial peptides have been identified as key components in innate host defense and as important contributors in maintaining health at mucosal barriers. Human β-defensins, a family of epithelial cell-derived cationic peptides (4-5 kDa), are known to exhibit both antimicrobial and immunomodulatory properties (Harder et al., (1997) Nature 387:861; Harder et al., (2001) J. Biol. Chem. 276:5707-13; Bowdish et al., (2006) Curr. Top. Microbiol. Immun. 306:27-66). Four human β-defensins have been identified thus far. Human β-defensins 1 (hBD-1) is constitutively expressed, whereas hBD-2 and -3 are inducible (Harder et al., (2001); Krasanaprakornkit et al., (1998) Infect. Immun. 66:4222-4228; Garcia et al., (2001) Cell Tissue Res. 306:257-264). All 3 peptides can be isolated from mucosal sites of the body. An hBD-4 transcript has also been described (Garcia et al. (2001) FASEB J. 15:1819-1821; Xu et al., (2006) Appl. Microbiol. Biotechnol. 72:471-479). hBDs have demonstrated activity against gram-positive and gram-negative bacteria, mycobacteria, fungi, and certain enveloped viruses at low micromolar concentrations (Yadava et al., (2006) Int. J. Antimicrob Agents 28:132-137; De Smet and Contreras (2005) Biotechnol. Lett 27:1337-1347). We recently showed that hBDs have antiretroviral activity by inhibiting HIV-1 infectivity of immunocompetent cells (Quinones-Mateu et al., (2003) Aids 17:F39-48; Feng et al., (2006) J. Immunol. 177:782-786). In addition, hBDs can enhance adaptive immunity by acting as adjuvant and chemoattracting T cells, immature dendritic cells, B cells, neutrophils, and macrophages (Yang et al., (1999) Science 286:525-528; Tani et al., (2000) Int. Immunol. 12:691-700; Oppenheimer et al., (2003) 62(Supp2); ii17-21). With new information emerging about these pluripotent peptides and their role in mucosal protection, diagnostic tools to quantify inducible β-defensins in body fluids and tissues are essential to better associate β-defensin expression with disease predisposition and progression.
Previous methods of quantifying human β-defensins in body fluids involved acid extraction followed by slot blot assays (Sahasrabudhe et al., (2000) 79:1669-1674; Tao et al., (2005) Antimicrob. Agents Chemother. 49:3883-3888), semiquantitative Western analysis (Mathews et al., (1999) 67:2740-2745; Chen et al., (2004) J. Cyst. Fibros. 3:45-50; Ross et al., (2004) Transplantation 78:1222-1224), or RIA (Hiratsuka et al., (2003) Thorax 58:425-430).